A new bone study is being planned that will measure the biomarker TRAP described in Exercise 6.17. Using the value of σ given there, 6.5 U/l, ?nd the sample size required to provide an estimate of the mean TRAP with a margin of error of 1.5 U/l for 95% con?dence.

Adjusting required sample size for drop out. Refer to the previous exercise. In similar previous studies, about 20% of the subjects drop out before the study is completed. Adjust your sample size requirement to have enough subjects at the end of the study to meet the margin of error criterion.